I've seen
oil squirt out of that hole on a Carter pump under hard driving. It was never more than a minor nuisence until the engine developed high blowby, than it really started spewing. It is a hole open to crankcase pressure after all. Why couldn't it be plugged? Even if the pump wasn't exposed to the volume of the crankcase I don't see the need for a tiny hole, it couldn't possibly contribute to venting. If it were lower and closer to the diaphram you could comtemplate it possibly draining fuel from a split diaphram but it's not.The only other fix would be a cute little breather:
